IPv6
+ Implement suggestions from http://www.kame.net/newsletter/19980604/
+ and ftp://ftp.iij.ad.jp/pub/RFC/rfc2553.txt
+
+ If a host has multiple addresses, then listen try to connect to all
+ in order until we get through. (getaddrinfo may return multiple
+ addresses.)
+
+ Possibly also when starting as a server we may need to listen on
+ multiple passive addresses. This might be a bit harder, because we
+ may need to select on all of them. Hm.
+
Define a syntax for IPv6 literal addresses. Since they include
colons, they tend to break most naming systems, including ours.
Based on the HTTP IPv6 syntax, I think we should use